Monomer flow rate, constant

Effect of the Polybutadiene Content. A series of ABS samples was prepared using 0.1 part TDM and varying the polybutadiene content from 5 to 50%. The introduction time of the monomers was a constant 3 hrs. When the polybutadiene content increased, the grafting efficiency increased from 2 to 40% (see Table V and Figure 3). One must note, however, that an increase in the polybutadiene content automatically decreases the monomer flow rate. It ensues that the curves in Figure 3 result from the simultaneous effects of two parameters, the polybutadiene content and the monomer flow rate. Nevertheless, it seems reasonable to think that the concomitant variations of these two parameters produce effects in the same direction. The polymer/monomer ratio increases when the polybutadiene content is increased and when the monomer flow rate is decreased. The grafting efficiency probably depends on this ratio, but the relative importance of the two parameters cannot be ascertained from our data. 

The results are summarized in Fig. 9 giving the relative abundance of the various ions at the end of the flow-tube as functions of the initial concentration of the monomer. From the decay of the signal of e/m = 69 (CF3 ) the rate constant of the bimolecular reaction... 

Surface plasmon resonance studies were employed to measure the equilibrium constants and association and dissociation rate constants of bisnaphthalimide derivatives (20, 21) with hairpin DNA immobilized on the metal surface.123 The equilibrium constants were higher and the dynamics slower for compounds 20 and 21 when compared to the equilibrium constants and dynamics of the model monomer (19). The values for ka and kd were determined from the change in the surface plasmon resonance signal when, respectively, the ligand solution was flowed over the... 

Later, Smith and coworkers succeeded in measuring rate constants of the reaction of MeLi with a carbonyl compound at various reagent concentrations with a stopped-flow/rapid scan spectroscopic method, and demonstrated that the reaction also exhibited a fractional kinetic order . Thus, the reaction of 2,4-dimethyl-4 -methylmercaptobenzophenone with MeLi in diethyl ether at 25 °C showed one-fourth order in MeLi in the concentration range of MeLi between 3.9 mM and 480 mM (Figure 1). The rate constant was 200 7 M s . Under these conditions, the monomer was considered the reactive species that exists in equilibrium with the tetramer. Addition of LiBr or Lil depressed the reaction rate but did not change the kinetic order. The same... 

The amount of a reagent consumed in the reactor is given by the mass balance, i.e. by the difference between the amounts flowing in and out, thus enabling the calculation of the required rate constants. For monomer, the mass balance becomes ... 

The rate constants of initiation of styrene by triflic acid are estimated to be roughly k,- 10 M sec-1 at 0° C in CH2CI2 this is 10,000 times smaller than the corresponding propagation rate constant under similar conditions [17]. However, it does not take into account the higher order kinetics in acid [134]. Initiation of more nucleophilic monomers is faster, with ki = 103 M l-sec-1 for a-methylstyrene [21] and kj = 5104 M -sec l for p-methoxystyrene [23], as determined by stopped-flow methods at ambient temperature in CH2CI2 and C2H4CI2. 

Sawamoto and Higadiimura have continued their investigation of the stop-flow spectroscopic behaviour of the polymerisation of p-methoxystyrene and added triflic acid to the series of catalysts previously tried. Again, they observed the typical absorption around 380 nm, attributed to the protonated monomer and calculated an initiaticm rate constant at 30 °C in ethylene chloride (assuming a bimolecular interaction orders not determined) kj = 5 x 10 s . This value is expectedly much... 

Rooney has recently revived work on this monomer in an investigation of its polymerisation by trityl hexafluoroantimonate - He used a spectroscopic stop-flow apparatus to follow initiation and an adiabatic calorimeter to measure rates of polymerisation. Propagation was shown to compete effectively with initiation to the point that some initiator was often present at the end of the polymerisations. These observations cast some doubts on the assumption made in the paper by the Liverpool school discussed above. A kinetic analysis of the initiation reaction showed it to be bimolecular, with a rate constant of about 130 sec at 20°C. The determination of the propagation rate constant was less strai tforward despite the fact that further monomer-addition experiments seemed to rule out any appreciable termination. The kp values fluctuated considerably as the initial catalyst concentration was varied, a fact which induced Rooney to propose that the empirical constant was a composite function of kp and kp. Experiments with a common-anion salt supported this proposal and their kinetic treatment led to the individual values of kp = 6 x 10 sec and kp = 5 x 10 sec. It is difficult to assess the reliability of these values in view of the following statement by the author the reaction at a 5 x 10 M concentration of initiator, thought to proceed exclusively through paired ions. .. . This statement is certainly incorrect as far as the initiator is concerned for which the proportion of ion pairs for a concentration 5 x 10 M at 20°C is only about 20% in methylene chloride However, the experiments... 

The implications of the correlation shown in Figure 8.7 are as follows (1) The energy input parameter (based on the luminous gas phase) does not control the deposition of material onto the cathode surface. (2) The current density of a DC glow discharge is the primary operational parameter. (3) The flow rate of monomer does not influence the film thickness growth rate. (4) The film thickness growth rate is dependent on the mass concentration of monomer (cM) in the cathode region rather than the mass input rate (FM). (In these experiments, the system pressure was maintained at a constant value of 50 mtorr, and thus c was a constant.)... 

Method II Closed System With Sorption of Monomer by a Porous Substrate. Monomer is fed into a closed system at a constant flow rate until the pressure of the system reaches a predetermined level. There is no monomer feed-in and no pumping during the glow discharge. 

Polymerization reactions require stringent operating conditions for continuous production of quality resins. In this paper the chain-growth polymerization of styrene initiated with n-butyllithium in the presence of a solvent is described. A perfectly mixed isothermal, constant volume reactor is employed. Coupled kinetic relationships descriptive of the initiator, monomer, polystyryl anion and polymer mass concentration are simulated. Trommsdorff effects (1) are incorporated. Controlled variables include number average molecular weight and production rate of total polymer. Manipulated variables are flow rate, input monomer concentration, and input initiator concentration. The... 

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